Romelu Lukaku also came to the fore for United – and he insists he always knew Gunners old boy Sanchez, who has struggled for form, would score at the Emirates.

“I told him yesterday he would score and he did today and I am really happy for him,” said the Belgian. “Because you know a lot of people tried to come at him, but today it was the success for us and I’m really delighted for him, with his performance.”

In the video above Lukaku also shares his thoughts on an incredible start as coach for Solskjaer, who stands clearly alone as having the best record to start a Manchester United managerial career.

Manchester United boss Ole Gunnar Solskjaer insists Alexis Sanchez can only improve after scoring on his Arsenal return.

Sanchez opened the scoring as United sealed a 3-1 win at Emirates Stadium to reach the fifth round of the FA Cup and extend Solskjaer’s winning start.

The two most successful sides in the competition’s history played out an entertaining Friday night cup tie which ended in a eighth-straight victory for the interim manager.

Goals from Sanchez and Jesse Lingard had set the visitors on course for victory before Pierre-Emerick Aubameyang pulled one back for the Gunners, only for substitute Anthony Martial to wrap up a comfortable win with a late strike.

Sanchez, fit again after a niggling hamstring problem, scored just his fifth United goal since leaving Arsenal for Old Trafford last January and was jeered all evening by the home supporters before being replaced.

Arsenal’s hopes of advancing in a competition they have won a record 13 times was dented by injuries to both of their starting central defenders.

Sokratis Papastathopoulos limped off in the first half with a twisted ankle before captain Laurent Koscielny – only recently back from a serious Achilles injury – was accidentally caught by the stray boot of United striker Romelu Lukaku.

Koscielny received eight minutes of treatment on the pitch and, while Gunners head coach Unai Emery did not have a detailed diagnosis, the injury could leave Arsenal’s captained sidelined once again.

“Maybe Laurent Koscielny is going to hospital to analyse what injury he has,” said the Spaniard.

“Maybe he’s broken (his cheek or jaw) but I hope not.

“I’m happy because I think our work is good, but the result is bad. Today it’s the result and the injuries. They don’t help us to be in the match, maybe when the result’s 1-2.

“In this moment we had the possibility to grow and to win, but these injuries – especially the one to Koscielny – didn’t help us because our rhythm went down.”

Paul Pogba is a leader and Solskjaer would have no hesitation handing him captaincy

Paul Pogba was told by Jose Mourinho that he was not fit to captain Manchester United – but Ole Gunnar Solskjaer sees the midfielder as a leader and would have no hesitation in handing him the armband.

The high of helping France to lift the World Cup over the summer was followed by a maddening few months at Old Trafford, where the 25-year-old grew unsettled as tension built with the manager.

Things seemed to come to a head in September as Mourinho told “second captain” Pogba he would not skipper United again in the build-up to the Carabao Cup defeat to Derby, with remarkable footage emerging the following day of a heated training-ground conversation between the pair.

Their relationship never recovered and the midfielder was not even getting minutes by the end of the Portuguese’s reign, never mind the armband.

But Pogba has been reborn under Solskjaer and has displayed leadership qualities, with video showing him geeing up team-mates before the Boxing Day win against Huddersfield – the second in their current run of seven straight wins in all competitions under the caretaker boss.